Magnetic control system



June 7, 1932. w, COOLEY 1,861,687

MAGNETIC CONTROL SYSTEM Original Filed Sept. 3, 1929 VOLT/162' INVENTOR.

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BY 6 041% A TTORNE;

cent material in a furnace for determining- Patented June 7, 1932 l y lUNITED STATES PATENT OFFICE WILLIAM B. COOLEY, OF MILWAUKEE, WISCONSIN,ASSIGNOR TO HEVI DUTY ELECTRIC COMPANY, OF MILWAUKEE, \VISCONSIN, ACORIORATION OF WISCONSIN MAGNETIC CONTROL SYSTEM Original applicationfiled September 3, 1929, Serial No. 390,162. Divided and thisapplication filed December 31, 1930.

My invention relates broadly to heat treatment furnaces and moreparticularly to a system for determining the condition of the materialunder heat treatment. It is a well established fact that the magneticcondition of steel is afiected by the application of heat 1 and that acertain relationship exists between r 1929, and entitled Magneticcontrol system.

One of the objects of my invention is to provide a system forelectrically determining the time at which magnetizable material treatedin a heat treatment chamber may reach a condition or reference point,from which subsequent operations can be determined, and where theelectrically determin ing means is operatively independent of the sourceof heat which may be supplied to the heat treatment chamber.

Another object of my invention is to provide a magnetic systempositioned adjacent material which is subjected to heat treatment in aheat treatment furnace, for determining the condition of the materialunder heat treatment operatively independent of the heat source which isapplied to the furnace.

Still another object of my invention is to provide a magnetic system.disposed adjathe condition of material which is subjected to heattreatment, the magnetic system being entirely independent of the heatingmeans which is supplied to the furnace.

A further object of my invention is to provide a magnetic systeminductively related to material in a furnace for determining thecondition of material which is being subject ed to heat treatment, andin combination therewith, but separate from the magnetic system, anothersystem for automatically controlling the temperature of the furnacewithout alfecting the magnetic system.

A still further object of my invention is Serial No. 505,862.

to provide a magnetic. system for controlling the time period over whichmaterial within the furnace is subjected to heat treatment in accordancewith the condition of the material within the furnace and independentlyof means by which the material in the furnace may be heated.

Other and further objects of my invention will be understood from thespecification hereinafter following by reference to the accompanyingdrawing which diagra1nmatically shows the arrangement of the parts ofthe furnace and circuit for indicating the magnetic permeability of thecharge under heat treatment therein.

My invention is directed to a magnetic indicator and control system forheat treatment furnaces, wherein the point at which the steel or othermagnetizable metal under heat treatment changes its magnetic propertiesupon heating, may be detected so that heating may be discontinued, orthe temperature modified, or the steel withdrawn, or permitted to remainin the furnace for definite subsequent periods at the discretion of theoperator. My

' invention makes use of the principle that steel or other magnetizablemetal changes its magnetic properties when heated to certaintemperature, depending upon the analysis of the steel. This change ofmagnetic properties, occurring at a positive transformation or criticalpoint in the steel, establishes when known, a refernce point in the heattreatment. My invention provides for magnetically determinin g the pointat which the steel or other metal under heat treatment changes itsmagnetic properties, or has reached a definite transformation point, sothat the proper heat treatment can be determined, the magneticdetermining means operating independently of the heating source.

In the system of my invention, a heat treatment furnace is provided withany form of heating means such as gas, or other fuel, or resistors whichare electrically energized. I provide a magnetic core of highpermeability which surrounds the refractory shell of the heat treatmentfurnace terminating in pole pieces aligned on opposite sides'of thecharge under heat treatment.

The pole pieces carry chamber 28.

electromagnetic windings which are connected in a power supply circuitthrough a coupling device. An indicating apparatus is connected incircuit with the coupling device. The magnetic path provided around themagnetic core is interrupted by the air gap across the furnace. \Vhenthe charge is introduced in this air .gap within the furnace, themagnetic conditions of the magnetic path through the core is changed.Pre'determine'd magnetizing force may be supplied to the magneticcircuit and calibrations placed upon the indicating apparatus showingthe normal magnetic readings when the charge is introduced into thefurnace. As the charge is subjected to heat treatment, a change in themagnetic properties occur which changes are readily observed by theindicating apparatus. As the charge approachesthe criticaltransformation point, the changes are detected by the indicatingapparatus and the character of subsequent heat treatment to be given tothe material within the chamber may b'e'determined.

Referring to the drawing in detail, the furnace chamber is designated at28 having a charge 29 shown schematically therein. An electric heatingsystem is shown including heating elements 4 arranged adjacent *thecharge in the furnace and energized from an. independent power supplysource which connects to terminals 5. The heating circuit is maintainedentirely separate and distinct from the magnetic measuring circuitshereina'fter described. The magnetic circuit is indicated as formedbycore 30 of high magnetic permeability terminating in pole pieces 31and 32 on opposite sides of the furnace These pole pieces are directlyaligned with the charge 29 within furnace chamber '28. Magneticwin-dings 31 and 34 are positioned upon. the pole pieces 31 an'd '32 forestablishing a permanent magnetic field through the furnace chamber withthecha rge 29 forming part of the :path thereof. The high magneticpermeability of the core 30 increases the strength of the magnetic fluxin thepaththrough the furnace chamber and renders slight variations dueto changes in the magnetic conditions of the charge 29 observable withgreat accuracy. A compensa tor connects between'the windings 35 and -34as shown at 12. The compensator 12 includes primary winding 15 andsecondary winding 14. The energizing circuit labeled line voltageconnects to one end of primary winding 15 and t-OOHQtLIXIlOf thQ winding34 on pole piece '32. The opposite end of winding 34 connects to theopposite end of primary Winding 15,'thus-completing the primary circuit.The secondary winding includes winding 14 o'fthe compensator12'connecte'dinseries through winding 35 on pole piece 3 l and inserieswith the indicator -16 returning tO the opposite end of the secondarywinding 14,

thus completing the secondary circuit. The compensator 12 has anadjustable core 17 for balancing purposes.

By the proper adjustment of the compensator which includes movable coremember 17, galvanometer 16 may be deflected to a predetermined or zerocondition indicating a position of balance of the magnetic flux throughthe furnace chamber without the charge 29 in position therein. Uponintroduction of the charge 29 the galvanometer or indicator 16 isdeflected by virtue of the increased flux which passes through thefurnace chamber in the path partially closed by the steel ormagnetizable charge 29. Under conditions of continued heat treatment,the charge 29 changes its magnetic properties and when thattransformation point is reached, the heating cycle "can be concluded, orthe operator, by noting the change of magnetic properties of the charge29 by reading the galvanometer 'or indicator 16, can cut off the sup-:ply of heating energy from the circuit 5 by any suitable means such asthe customary switch, 'orzhe may elect to soak the charge for anysubsequenttime.

While I have described my invention in-one of its preferred embodiments,I desire that it is understood that modifications may be made and thatno limitations upon my invention are intended other than are imposed bythe scope of the appended claims.

What I claim as :new and desire to secure by Letters Patent-of theUnited States is as follows:

1 A furnace comprising a chamber adapted to receive a charge, a heatingelement in said chamber, a source of electric "current, a primaryandsecondaiy'coil having a common core of material of high permeability,an air gap in the magnetic circuit so disposed that the lines of forcepass through the charge within said chamber, and means responsive toinductive effects of the primer c'oi'l and con'neoted with saidsecondary coll :foriindicating the magnetic properties ofsaid changeduring the heating process.

2. A magnetic control system for heat treatment furnaces comprising incombination with "a furnace chamber adapted to :re-

oeive a charge for "heat :treatment, heating means within said chamber,a magnetic core memberextending exteriorly of said chamber andterminating in pole pieces aligned with the charge within said chamber,magnetic "windings disposed'on saidipole piecesyacompensatorhavingapair-of windings connect- :ed in circuitwith themagnetic windings on'saidpole pieces, a source of potentialin circuit withone of thewindings of said pair of windings, 'and an indicator connected incircuit 'With the other of said windings of :saidip'air ofxwindings iforindicating theimagnetic permeability "of the charge within the furnaceduring the :processof-heat treatment. 139

3. A furnace comprising in combination a heating chamber adapted toreceive a charge of magnetic material disposed within said chamber,heating means for said charge within the chamber, a magnetic coreextending around said chamber and terminating in a pair of pole piecesexterior of said chamber and aligned with said charge whereby saidcharge forms a portion of a path for magnetic flux through said core,electromagnetic windings on said pole pieces, a compensator having aprimary and secondary winding, a source of potential in circuit withsaid primary winding and one of said electromagnetic windings, a meterconnected in circuit with said secondary winding and the other of saidelectromagnetic windings for indicating changes in the magneticcondition of the charge within the furnace during the heat treatmentprocess.

4:. A furnace including a heat treatment chamber adapted to receive acharge of magnetizable material, means for heating said charge, amagnetic core member extending around said chamber and terminating inoppositely disposed pole pieces directed toward each other and alignedwith said charge whereby said charge forms a part of a path for magneticlines of force through said core, a source of potential, a compensatorhaving a pair of inductively related windings, an indicating meter,electromagnetic windings on said pole pieces and series connectedcircuits each individual to one of the windings on said compensator andone of the electromagnetic windings on said pole pieces, one of saidcircuits having a connection to said source, and the other of saidcircuits having a connection to said meter for indicating on said meterthe change of magnetic properties of said charge during the heattreatment process.

5. In an electric furnace, a heat treatment chamber adapted to receive acharge of magnetizable material, means for heating said charge, amagnetic core extending around said chamber and terminating in polepieces directed toward said charge in alignment one with the-other, amagnetic compensator including a pair of inductively relatedelectromagnetic windings on said pole pieces, a source of potential, acircuit connection between one of the windings of said compensator andone of the electromagnetic windings on said pole pieces with said sourceof potential and another circuit connection between the other winding ofsaid compensator and the electromagnetic winding on the other of saidpole pieces with a meter for indicating on said meter changes in themagnetic properties of said charge.

In testimony whereof I afiix my signature.

WILLIAM B. GOOLEY.

